RADICAL-TYPE CYCLIZATION OF DIENS .6. TOT AL SYNTHESIS OF (-)-COROLINAND (-)-EPICORIOLIN FROM (S)-(-CARVONE())

l-3,3a,4,6a-tetrahydro-2H-cyclopenta[b]furan-2-one (10) and imethyl-3- methylene-2H-cyclopenta[a]pentalen-2-one (21) are the key intermediate s in the synthesis of the title compounds 1 and 1a. Enantiomerically p ure 10 is produced from (S)-(+)-carvone (4) in seven straightforward r eactions. Compound 21 is produced from 10 by analogy with the method d eveloped for the synthesis of (-)-hirsutene. Through the introduction of the double bond into 21 via the silylenolether 23 one arrives at pr ecoriolin 25, which is converted into (-)-coriolin (1) and the C-3 epi mer (-)-epicoriolin (1a) (63:37) with hydrogen peroxide. The structure s of 1 and 1a were confirmed via X-ray crystallography.